Water-cooled viscous coupling

ABSTRACT

A viscous coupling includes an input and an output member which define a shear space therebetween. Viscous fluid in the shear space operates to transmit torque between the input and output members. When torque is transmitted between the input and output members, heat is generated. One of the members has a cooling medium chamber to receive a cooling medium from a cooling medium conduit. The conduit is positioned substantially in alignment with the rotational axis of the input and output members. The cooling medium gravitates toward the outer peripheral surfaces of the cooling medium chamber and vaporizes upon application of sufficient heat thereto. The vapor gravitates toward the rotational axis of the members and is subsequently cooled.

United States Patent Thompson [21] Appl. No.: 878,136

[52] 11.5. C1. ..192/58 B, l23/41.l1, l23/41.46, 165/105,192/113 B [51]Int. Cl. ..Fl6d 35/00, Fl6d 13/72 [58] FleldofSearch ..192/58 A,58 8,58C, 113 B, 192/82 '1; 123141.11, 41.12, 41.46; 165/105 [56] ReferencesCited UNITED STATES PATENTS 2,633,697 4/1953 Johnson... .....l92/82 T UX2,743,384 4/1956 Turner ..l65/105 UX 2,988,188 6/1961 Tauschek........l92/58 CX 3,151,669 10/1964 Quenneville ..165/105 X 3,272,188 9/1966Sabat ..l92/58 A 3,505,982 4/1970 Walter et al...... ...123/4 1.12

[ 51 May 9, 1972 2,852,118 9/1958 Lacroix, Jr. et a1. ..192/113 B2,982,377 5/1961 Eames 3,512,622 5/1970 Sutaruk 192/58 B PrimaryE.\'aminerAllan D. Herrmann Attorney-Yount and Tarolli ABSTRACT Aviscous coupling includes an input and an output member which define ashear space therebetween. Viscous fluid in the shear space operates totransmit torque between the input and output members. When torque istransmitted between the input and output members, heat is generated. Oneof the members has a cooling medium chamber to receive a cooling mediumfrom a cooling medium conduit. The conduit is positioned substantiallyin alignment with the rotational axis of the input and output members.The cooling medium gravitates toward the outer peripheral surfaces ofthe cooling medium chamber and vaporizes upon application of sufficientheat thereto. The vapor gravitates toward the rotational axis of themembers and is subsequently cooled.

11 Claims, 3 Drawing Figures FIG. 1

//Vl/E/VTO/? OWEN R. THOMPSON WJJM WATER-COOLED VISCOUS COUPLING Thepresent invention relates to a viscous coupling having an input memberand an output member defining a fluid shear space therebetween andbetween which torque is transmitted by fluid in the shear space, andparticularly relates to a viscous coupling having improved means fordissipating heat generated by transmission of torque between the inputand output members.

Viscous couplings are commonly used for driving a cooling fan associatedwith the engine of an automobile. Automobile engine fan coolingrequirements have been increasing because of the increasing horsepowerof engines, reduced frontal or ram air area, and smog control heatloads. As a result of these increases in fan cooling requirements,design changes have been made in the viscous couplings for driving afan.

The major problem in the development of a viscous coupling to handlethese higher fan cooling requirements is the dissipation of heatgenerated by the transmission of torque between the coupling members. Byreducing the internal temperature of a viscous coupling, bearing life islengthened and temperature-sensitive mechanical fluids for transmittingtorque between the coupling members survive. As a result, the viscouscoupling has a longer life and has a greater torquetransmittingcapability. In fact, by dissipating the heat effectively, a greatertorque-carrying capacity will be realized in equal or even smaller sizedviscous couplings.

It is to be understood that the less the temperature of a viscouscoupling increases, the more effective the coupling is. When thetemperature of a viscous coupling increases, the viscosity of the fluidin the shear space between the input and output members of the viscouscoupling decreases. Thus, a greater shear area to transmit an equivalentamount of torque is required. By maintaining the viscous coupling at alower temperature, it is possible to provide greater torque-carryingcapacities in the coupling by maintaining the viscous fluid at a higherviscosity. Moreover, the life of the bearings associated with thecoupling is increased when the viscous coupling is effectively cooled.

The present invention provides a new and improved viscous couplinghaving means for dissipating heat generated in the viscous coupling whentorque is transmitted between the input and output members of thecoupling. The heat is dissipated by providing a liquid cooling medium ina chamber of one of the members of the coupling and providing forcooling the liquid cooling medium after it has absorbed heat.

When such a liquid-cooled viscous coupling is used in conjunction with aliquid-cooled engine, the cooling medium used to cool the engine mayalso be used to cool the coupling. Moreover, when such an engine isequipped with a pump, it is possible to provide the cooling medium tothe viscous coupling under pressure and maintain a pressure in thecooling medium chamber. By maintaining the cooling medium in the chamberunder pressure, a greater quantity of heat is required to vaporize thecooling medium. Thus, the effectiveness of such a cooling system isfurther increased.

The viscous coupling of the present invention includes a conduit havingan axis substantially co-extensive with the rotational axis of the inputand output coupling members. The cooling medium tends to flow along theperipheral surface of the conduit into the cooling medium chamber, dueto the centrifugal force created by rotation of the conduit with themember in which the cooling medium chamber is positioned. Uponvaporization of the cooling medium in the chamber, the vapor gravitatestoward the center of the chamber and flows to a central location in theconduit where the vapor is condensed by contact with and/or cooling bythe liquid cooling medium. Such a construction efficiently cools thevapor produced by evaporation of the cooling medium and preventstemperature-sensitive mechanical fluids from breaking down.

Accordingly, it is an object of the present invention to provide a newand improved viscous coupling constructed to effectively dissipate heatgenerated by the shear of a viscous fluid when torque is transmittedbetween the input and the output members of the viscous coupling,thereby increasing the torque-transmitting capability of the coupling.

Another object of the present invention is the provision of a new andimproved viscous coupling having input and output members defining ashear space therebetween and between which torque is transmitted byviscous fluid in the shear space and wherein the viscous couplingincludes means providing for liquid cooling thereof.

Yet another object of the present invention is the provision of anapparatus for transmitting torque having an input member and an outputmember in which one of the members has a chamber for receiving a liquidcooling medium and wherein the cooling medium vaporizes upon sufficientheating and gravitates to the rotational center of the chamber such thatliquid cooling medium is always maintained in contact with the outerperipheral surface of the chamber.

A further object of the present invention is the provision of a new andimproved apparatus for transmitting torque having an input member and anoutput member and wherein one of the members is adapted to dissipateheat generated by the transmission of torque between the input andoutput members and has a chamber for receiving a cooling medium underpressure which vaporizes upon sufficient heating and gravitates to thecenter of the chamber.

Yet another object of the present invention is the provision of a newand improved apparatus for transmitting torque between an input memberand an output member wherein one of the members is adapted to dissipateheat generated by the transmission of torque between the input andoutput members and has a chamber for receiving cooling medium from aconduit whereby the heat vaporizes the cooling medium and the vaporgravitates to the center of the chamber where it is cooled.

Further objects and advantages of the present invention will be apparentto those skilled in the art to which it relates from the followingdetailed description of embodiments of the present invention made withreference to the accompanying drawings in which:

FIG. 1 is a cross-sectional view of an apparatus embodying the presentinvention;

FIG. 2 is a partial cross-sectional view of a modified apparatusembodying the present invention; and

FIG. 3 is a partial cross-sectional view of a still further modifiedapparatus embodying the present invention.

The present invention provides an improved viscous coupling having aninput member and an output member with an improved means for dissipatingheat created due to the transmission of torque therebetween. In general,one of the members has a chamber for receiving a liquid cooling medium.The cooling medium vaporizes upon receiving sufficient heat and which,upon vaporization, gravitates to the center of the chamber and issubsequently cooled. By effectively cooling the viscous coupling of thepresent invention, the life of the bearings of the coupling arelengthened and the torquecarrying capacity of the viscous coupling maybe substantially increased. The present invention may be applied toviscous coupling of a wide variety of constructions and uses and forpurposes of illustration is described and illustrated in the drawings asapplied to a viscous coupling 10, as shown in FIG.

The viscous coupling 10 is illustrated as associated with an internalcombustion engine of an automobile. In order to cool such an internalcombustion engine, a water pump, partially shown at 20, is provided tocirculate a cooling medium, such as water, around the motor to absorbthe heat created by the combustion in the motor in a manner well knownto those skilled in the art. To cool this cooling medium or water, aradiator is generally provided having a plurality of thin tubes throughwhich the heated water flows. Air is forced through the radiator to coolthe water and provide a supply of cooled water to the water pump 20 forrecirculation through the motor.

in order to draw air through the radiator, a fan 22 is driven by theviscous coupling 10 from the motor. The fan pulls air through theradiator and thereby assists the air forced through the radiator by theforward translational movement of the vehicle to provide a sufficientamount of air flowing through the radiator to effect cooling of thewater, as is known.

It should be understood that the viscous coupling is ideally suited formoving air through a radiator, since the fan is required to move moreair through the radiator when the car is not in motion or when the caris traveling at a relatively low speed. A characteristic of the viscouscoupling 10 is that the rotational output speed of the viscous couplingwill not increase proportionally with an increase in the input speed ofthe viscous coupling. Accordingly, as the speed of the vehicleincreases, the fan is not driven at a proportionally increased speed.This is ideal, since more ram air is provided through the radiator andsince the exposed frontal area allows air to flow through the radiatoras the speed of the vehicle increases.

The viscous coupling 10 includes an input coupling member 14 and anoutput coupling member 12. The fan 22 is suitably secured to the outputcoupling member 12 and rotated upon rotation of the output member 12.The output member 12 is driven by the action of viscous shear fluidlocated between the input and output members, as will be discussedbelow. The input member 14 is drivingly connected to a drive member 28.Drive pulleys 26 are connected to the drive member 28, and belts 24 aretrained around the pulleys 26 and rotate the pulleys. The belts aresuitably driven from the crankshaft of the engine.

As noted above, the drive between the input and output members 14, 12 iseffected by the action of viscous shear fluid positioned therebetween.The output member 12 has a plurality of grooves 30 therein in whichportions 32 of the input member 14 are received, as is known. Thesurfaces of the input member are spaced slightly from the surfaces ofthe output member to provide a fluid shear space therebetween. Theviscous fluid is contained in the shear space and is in contact with theinput and output members 14, 12, respectively. When the input member 14is rotated, the viscous fluid contained in the grooves 30 transmitstorque to the output member 12 to which the fan 22 is attached. Theoutput member 12 is rotatably mounted on the drive member 28 by bearing34 such that the output member 12 may rotate relative to the inputmember 14 about a common rotational axis 56.

Heat is generated when the viscous fluid in the shear space is shearedduring transmission of the torque between the input member 14 and theoutput member 12. This heat, of course, decreases the viscosity of theviscous fluid. As the viscosity of the fluid decreases, the coupling 10transmits less torque from the input member 14 to the output member 12and, thus, rotates the fan 22 at proportionally slower speed withrespect to the speed of the motor.

The generation of this heat effects not only the capability of theviscous fluid to transmit torque, but also efiects bearing life andoverall effectiveness and durability of the viscous coupling. Theseproblems are becoming more acute due to the increased torque demands forviscous couplings. This demand results from increased engine horsepower,reduced frontal area, and smog control heat loads. In order toeffectively handle these demands, it is necessary to provide for moreeffective dissipation of heat generated by a coupling than is possiblewith known techniques for heat dissipation in viscous couplings.

In order to dissipate heat generated by the transmission of torquebetween the coupling members 14, 12, one of the members is constructedso as to be liquid cooled. In the illustrated embodiment, the inputmember 14 is provided with a cooling medium chamber 16. The chamber 16in the input member 14 is provided with a cooling medium through aconduit 18. The input member 14 includes a body 35 and a cover member38. The chamber 16 is defined by the outer surface 36 of the body 35 andthe cover 38 secured to the body 35. The outer surface 36 of the inputmember 14 extends circumferentially about the rotational axis of theviscous coupling 10. The cover 38 is positioned against a surface 40 onthe body 35. A portion 42 of the body 35 is rolled over the outside ofthe cover 38 to retain the cover 38 with respect to the surface 40 ofthe body 35. This connection eflects a fluid-tight seal which is simpleto manufacture and provides a chamber for receiving the cooling mediumfor efficiently cooling the viscous coupling 10.

The cooling medium is received by the chamber 16 through the conduit 18.The conduit 18 includes the drive member 28, which is hollow, and theconduit member 44. The conduit member 44 is connected with the drivemember 28 by means of a press fit therebetween. Sealing means 46, 48 areprovided to seal the conduit member 44 and drive member 28 to prohibitleakage of the cooling medium from the conduit 18.

The cooling medium in the illustrated embodiment comprises the coolingmedium which is in the cooling system of the vehicle and would comprisewater or a mixture of water, antifreeze, additives, or the like. Theconduit 44 communicates with the water pump 20 and receives coolingmedium therefrom. The pump 20 includes a housing member 50 mounted onthe engine and rotatably supports the conduit member 44 therein by meansof bearings 52. An impeller 54 of the pump 20 is drivingly connected tothe conduit member 44 and is rotated by the conduit member 44 which isdriven from the pulleys 26. The impeller 54 of the pump 20 pressurizesthe cooling medium. The pressurized fluid is directed into the end ofthe conduit member 44 secured to the impeller 54 and flows therealonginto the chamber 16 to cool the viscous coupling 10. When the coolingmedium 16 is heated sufficiently, it vaporizes in the chamber 16. Thevapor will gravitate toward the rotational axis 56 of the chamber 16,connecting member 28 and conduit member 44, and the liquid coolingmedium is forced toward the outer walls of the conduit 18 due to thecentrifugal force acting thereon. The vapor gravitates or is displacedtoward the center or rotational axis of the viscous coupling and isillustrated at 60 in the drawing. The cooling medium in contact with thevapor will cool and condense the vapor.

When the vapor is formed from the cooling medium, the cooling mediummust receive its latent heat of vaporization from the coupling in orderto vaporize and must give up the latent heat of vaporization to theliquid cooling medium in order to condense. Thus, by such a heattransfer process, the viscous coupling 10 is effectively and efficientlycooled. It should be understood that the greater the pressure at whichthe cooling medium is supplied, the higher the temperature that isrequired to vaporize the cooling medium.

In the event that a substantial volume of heat is generated whichresults in substantial amounts of vapor being created, the vapor mayreturn through the conduit 44 to the pump 20 and be condensed in thepump 20. In such a case, fluid would flow from the pump 20 through theconduits 44, 18 into the cooling medium chamber 16 while vapor isflowing in the opposite direction. This is possible due to the fact thatthe fluid medium being heavier hugs the walls of the conduits 44, 18,while the vapor moves through the central portion thereof, as notedabove.

A second embodiment of a liquid-cooled viscous coupling is shown in FIG.2 having a similar construction to the coupling shown in FIG. 1. Forease of description, common reference numerals will be used indescribing the viscous coupling of the second embodiment with the suffixa appended thereto. It should be understood that the viscous coupling100, as shown in FIG. 2, is of similar construction to the viscouscoupling shown in FIG. 1, and to simplify description thereof only thestructural differences will be hereafter described.

In the embodiment of FIG. 2, in order to carry the vapor away from thechamber 16a and condense the vaporized cooling medium, a tube 62 isprovided having a centrally located bore therein. The tube 62 issupported in the conduit 18a by support members 63. The support members63 allow the cooling medium to flow along the conduit 18a outside thetube 62 while supporting the tube 62. The tube 62 is in axial alignmentwith the rotational axis 560 of the input member 14a, output member 12aand conduit 18a. As the cooling medium flows through the conduit 18atoward the chamber 16a, the vapor moves along the tube 62 away from thechamber 16a. The cooling medium thus surrounds the vapor contained inthe tube 62 and cools and condenses it throughout the entire length ofthe tube 62a. This provides for effective heat transfer and condensationof the vapor in the tube 62.

A third embodiment of the viscous coupling is shown in FIG. 3 alsohaving a similar construction to the coupling shown in FIG. 1. Again forease of description, common reference numerals will be used indescribing the viscous coupling of the embodiment of FIG. 3 with thesuffix b appended thereto. It should be understood that the viscouscoupling 10b, as shown in FIG. 3, is of a similar construction to theviscous coupling shown in FIG. 1, and to simplify description thereof,only the structural differences will be described below.

In the embodiment of FIG. 3, a tube 64 is located along the rotationalaxis 56b and has a portion 66 extending into the cooling medium chamber16b. The tube 64 is supported in the conduit 180 by support means 65, asshown in the embodiment of FIG. 2. The supports 65 allow the coolingmedium to flow along the conduit 18a while supporting the tube 64. Whenthe cooling medium in the chamber 16b vaporizes, it will gravitatetoward the rotational axis 56b of the chamber 16b. Since the portion 66of the tube 64 extends into the chamber 16b, the vapor will be receivedby the tube 64 and will gravitate or be pumped through the end of thetube 66 and along the tube 64 by the rotation of the tube, due to thelower gravity at the rotational axis 56b. The cooling medium surroundsthe vapor contained in the tube 64 and cools and condenses the vapor asit moves through the tube 64. This provides for an effective heattransfer to condense the vapor in the tube 64.

It is apparent from the above that the present invention provides a newand improved viscous coupling which includes input and output members14, 12, respectively. The input and output members 14, 12, respectively,define a shear space therebetween so that a viscous fluid in the shearspace transmits torque from the input member 14 to the output member 12.The transmission of torque between the input and output members 14, 12,respectively, results in the generation of heat. The input member 14 hasa chamber 16 for receiving a cooling medium which dissipates at least aportion of the heat generated. The cooling medium vaporizes uponapplication of the heat thereto and conduit means 18 directs the coolingmedium into the chamber 16 and provides for cooling of the vaporizedcooling medium. As a result of this structure, effective cooling can beprovided, and a viscous coupling having a long life and a hightorque-transmitting capability is provided. In fact, couplings of thisconstruction may transmit torque only capable of substantially largerviscous couplings of known constructions.

Having described my invention, what I claim is:

1. A coupling apparatus comprising relatively rotatable input and outputmembers, said input and output members defining a shear spacetherebetween, a viscous fluid in said shear space for transmittingtorque between said input and output members with transmission of torqueresulting in the generation of heat in said viscous fluid, said viscousfluid being of the type which decreases in viscosity with temperatureincreases, one of said members having a chamber for receiving a coolingliquid for absorbing and dissipating a portion of the generated heatfrom said viscous fluid, said cooling liquid being vaporizable at thenormal operating temperature of said viscous fluid, and conduit meansfor directing the cooling liquid into said chamber and said vapor fromsaid chamber for condensation thereof to liquid, whereby the change inphase of said cooling liquid from liquid to vapor and condensation backto liquid results in dissipation of a substantial amount of thegenerated heat.

2. An apparatus as defined in claim 1 including a pump in fluidcommunication with said conduit meansfor supplying the cooling liquid tosaid chamber, and said conduit means comprising a hollow drive shaft fordriving said one member having said chamber and rotatable therewith.

3. An apparatus as defined in claim 2 wherein the rotational axis ofsaid conduit means is substantially coaxial with the rotational axis ofsaid one member having said chamber therein, said one member having anouter surface defining said chamber adjacent the shear space between thecoupling members for receiving said heat, said cooling liquid beingforced outwardly toward the outer surface of said one member and saidvapor being displaced inwardly toward the axis of rotation of said onecoupling member upon rotation thereof.

4. An apparatus comprising relatively rotatable input and outputmembers, said input and output members defining a viscous fluid shearspace therebetween, viscous fluid of the type which decreases inviscosity with temperature increases located in said shear space fortransmitting torque between said input and output members, thetransmission of torque between said input and output members resultingin generation of heat in said viscous fluid, said input coupling memberdefining a chamber for receiving a cooling liquid for dissipating atleast a portion of the heat, said shear space being located radiallyoutwardly of the axis of rotation of the input coupling member, saidchamber having a wall surface adjacent said shear space, said coolingliquid being forced to move radially outwardly of said chamber uponrotation of said input coupling member and into contact with said wallsurface to absorb heat therefrom, said cooling liquid vaporizing uponthe heat being applied thereto at said wall surface and the vapor beingdisplaced inwardly by said cooling liquid toward the axis of rotation ofthe input coupling member, and conduit means for directing coolingliquid into said chamber and vapor therefrom for condensation thereof.

5. An apparatus as defined in claim 4 further including a pump, saidconduit means including a hollow drive shaft communicating with saidpump to direct cooling liquid into said cooling chamber.

6. A torque transmitting mechanism comprising a rotatable input member,a rotatable output member, and a torque transmitting interfacetherebetween, said torque transmitting interface allowing slippage ofsaid members relative to each other during transmission of torquetherebetween causing heat to be generated at said torque transmittinginterface during operation of said torque transmitting mechanism,

one of said members including a chamber having a first portion adjacentsaid torque transmitting interface and a second portion remote from saidtorque transmitting interface radially inwardly of said first portion,

a liquid cooling medium disposed in said chamber, said liquid coolingmedium being vaporizable at the normal operating temperature of saidtorque transmitting interface for cooling said interface, said vaporizedcooling medium being displaced inwardly toward the axis of rotation ofsaid one member into said second portion of said chamber, a source ofsaid cooling medium, and conduit means extending from said source intothe second portion of said chamber to continuously supply liquid coolingmedium into said second chamber during operation of said mechanism andfor conducting said vapor from said chamber for condensation thereof toliquid by the flow of liquid cooling medium thereinto.

7. An apparatus comprising relatively rotatable input and outputmembers, said input and output members defining a shear spacetherebetween so that a viscous fluid in said shear space transmitstorque between said input and output members, the transmission of torquebetween said input and output members resulting in the generation ofheat, one of said members having a chamber for receiving a coolingmedium for dissipating at least a portion of the generated heat, conduitmeans having a passageway for directing the cooling medium into saidchamber, 1

said cooling medium vaporizing upon heat being applied thereto, saidconduit providing cooling medium for cooling said vapor,

and a tube located in said passageway, said tube having a bore thereinfor receiving the vapor from said chamber.

8. An apparatus as defined in claim 7 wherein said tube is located insaid passageway and the cooling medium in said passageway cools andcondenses said vapor received by said tube from said chamber.

9. An apparatus. comprising relatively rotatable input and outputmembers, said input and output members defining a shear spacetherebetween so that a viscous fluid in said shear space transmitstorque between said input and output members, the transmission of torquebetween said input and output members resulting in the generation ofheat, one of said members having a chamber for receiving a coolingmedium for dissipating at least a portion of the generated heat, andconduit means for directing the cooling medium into said chamber,

said cooling medium vaporizing upon heat being applied thereto, saidconduit providing cooling medium for cooling said vapor,

said conduit means being connected with said one member having saidchamber and adapted to rotate therewith,

the rotational axis of said conduit means being substantiallycoextensive with the rotational axis of said one member having saidchamber therein, said one member having an outer surface defining saidchamber adjacent the shear space between the coupling members forreceiving said heat, said cooling medium gravitating toward the outersurface of said one member and said vapor gravitating toward the centerof said chamber upon rotation of said one member,

said conduit means including a tube having a bore therein,

said tube being positioned inside said passageway for receiving saidvapor and having a longitudinal axis substantially coextensive with saidrotational axis of said one member having said chamber therein andconducting the vapor therealong from said chamber for cooling said vaporwith the cooling medium in said conduit. 10. An apparatus as defined inclaim 9 wherein said tube includes a portion extending radially from thelongitudinal axis of said tube and into said chamber for receiving thevapor and pumping the vapor along the bore of said tube away from saidchamber.

11. An apparatus comprising relatively rotatable input and outputmembers, said input and output members defining a viscous fluid shearspace therebetween, the transmission of torque between said input andoutput members resulting in generation of heat, said input memberdefining a chamber for receiving a cooling medium for dissipating atleast a portion of the heat, said shear space being located radiallyoutwardly of the axis of rotation of the input coupling member, saidcooling medium tending to move radially outwardly of said chamber uponrotation of said input member and said cooling medium vaporizing uponthe heat being applied thereto and the vapor tending to be disposedalong the axis of rotation of the input member, a hollow drive shaft fordriving said input member, said hollow shaft communicating with saidchamber for directing coolant into said chamber and providing forremoval of said vapor from said chamber, and

a water pump communicating with said hollow shaft to provide apressurized cooling medium in said coolin chamber,

said hollow drive shaft having a tube supported centrally thereof forconducting vapor from said chamber, said vapor being cooled by thecooling medium in the hollow drive shaft externally of the tube.

1. A coupling apparatus comprising relatively rotatable input and outputmembers, said input and output members defining a shear spacetherebetween, a viscous fluid in said shear space for transmittingtorque between said input and output members with transmission of torqueresulting in the generation of heat in said viscous fluid, said viscousfluid being of the type which decreases in viscosity with temperatureincreases, one of said members having a chamber for receiving a coolingliquid for absorbing and dissipating a portion of the generated heatfrom said viscous fluid, said cooling liquid being vaporizable at thenormal operating temperature of said viscous fluid, and conduit meansfor directing the cooling liquid into said chamber and said vapor fromsaid chamber for condensation thereof to liquid, whereby the change inphase of said cooling liquid from liquid to vapor and condensation backto liquid results in dissipation of a substantial amount of thegenerated heat.
 2. An apparatus as defined in claim 1 including a pumpin fluid communication with said conduit means for supplying the coolingliquid to said chamber, and said conduit means comprising a hollow driveshaft for driving said one member having said chamber and rotatabletherewith.
 3. An apparatus as defined in claim 2 wherein the rotationalaxis of said conduit means is substantially coaxial with the rotationalaxis of said one member having said chamber therein, said one memberhaving an outer surface defining said chamber adjacent the shear spacebetween the coupling members for receiving said heat, said coolingliquid being forced outwardly toward the outer surface of said onemember and said vapor being displaced inwardly toward the axis ofrotation of said one coupling member upon rotation thereof.
 4. Anapparatus comprising relatively rotatable input and output members, saidinput and output members defining a viscous fluid shear spacetherebetween, viscous fluid of the type which decreases in viscositywith temperature increases located in said shear space for transmittingtorque between said input and output members, the transmission of torquebetween said input and output members resulting in generation of heat insaid viscous fluid, said input coupling member defining a chamber forreceiving a cooling liquid for dissipating at least a portion of thehEat, said shear space being located radially outwardly of the axis ofrotation of the input coupling member, said chamber having a wallsurface adjacent said shear space, said cooling liquid being forced tomove radially outwardly of said chamber upon rotation of said inputcoupling member and into contact with said wall surface to absorb heattherefrom, said cooling liquid vaporizing upon the heat being appliedthereto at said wall surface and the vapor being displaced inwardly bysaid cooling liquid toward the axis of rotation of the input couplingmember, and conduit means for directing cooling liquid into said chamberand vapor therefrom for condensation thereof.
 5. An apparatus as definedin claim 4 further including a pump, said conduit means including ahollow drive shaft communicating with said pump to direct cooling liquidinto said cooling chamber.
 6. A torque transmitting mechanism comprisinga rotatable input member, a rotatable output member, and a torquetransmitting interface therebetween, said torque transmitting interfaceallowing slippage of said members relative to each other duringtransmission of torque therebetween causing heat to be generated at saidtorque transmitting interface during operation of said torquetransmitting mechanism, one of said members including a chamber having afirst portion adjacent said torque transmitting interface and a secondportion remote from said torque transmitting interface radially inwardlyof said first portion, a liquid cooling medium disposed in said chamber,said liquid cooling medium being vaporizable at the normal operatingtemperature of said torque transmitting interface for cooling saidinterface, said vaporized cooling medium being displaced inwardly towardthe axis of rotation of said one member into said second portion of saidchamber, a source of said cooling medium, and conduit means extendingfrom said source into the second portion of said chamber to continuouslysupply liquid cooling medium into said second chamber during operationof said mechanism and for conducting said vapor from said chamber forcondensation thereof to liquid by the flow of liquid cooling mediumthereinto.
 7. An apparatus comprising relatively rotatable input andoutput members, said input and output members defining a shear spacetherebetween so that a viscous fluid in said shear space transmitstorque between said input and output members, the transmission of torquebetween said input and output members resulting in the generation ofheat, one of said members having a chamber for receiving a coolingmedium for dissipating at least a portion of the generated heat, conduitmeans having a passageway for directing the cooling medium into saidchamber, said cooling medium vaporizing upon heat being applied thereto,said conduit providing cooling medium for cooling said vapor, and a tubelocated in said passageway, said tube having a bore therein forreceiving the vapor from said chamber.
 8. An apparatus as defined inclaim 7 wherein said tube is located in said passageway and the coolingmedium in said passageway cools and condenses said vapor received bysaid tube from said chamber.
 9. An apparatus comprising relativelyrotatable input and output members, said input and output membersdefining a shear space therebetween so that a viscous fluid in saidshear space transmits torque between said input and output members, thetransmission of torque between said input and output members resultingin the generation of heat, one of said members having a chamber forreceiving a cooling medium for dissipating at least a portion of thegenerated heat, and conduit means for directing the cooling medium intosaid chamber, said cooling medium vaporizing upon heat being appliedthereto, said conduit providing cooling medium for cooling said vapor,said conduit means being connected with said one member having saidchamber and adapted to rotate therewith, the rotational axis of saidconduit Means being substantially coextensive with the rotational axisof said one member having said chamber therein, said one member havingan outer surface defining said chamber adjacent the shear space betweenthe coupling members for receiving said heat, said cooling mediumgravitating toward the outer surface of said one member and said vaporgravitating toward the center of said chamber upon rotation of said onemember, said conduit means including a tube having a bore therein, saidtube being positioned inside said passageway for receiving said vaporand having a longitudinal axis substantially coextensive with saidrotational axis of said one member having said chamber therein andconducting the vapor therealong from said chamber for cooling said vaporwith the cooling medium in said conduit.
 10. An apparatus as defined inclaim 9 wherein said tube includes a portion extending radially from thelongitudinal axis of said tube and into said chamber for receiving thevapor and pumping the vapor along the bore of said tube away from saidchamber.
 11. An apparatus comprising relatively rotatable input andoutput members, said input and output members defining a viscous fluidshear space therebetween, the transmission of torque between said inputand output members resulting in generation of heat, said input memberdefining a chamber for receiving a cooling medium for dissipating atleast a portion of the heat, said shear space being located radiallyoutwardly of the axis of rotation of the input coupling member, saidcooling medium tending to move radially outwardly of said chamber uponrotation of said input member and said cooling medium vaporizing uponthe heat being applied thereto and the vapor tending to be disposedalong the axis of rotation of the input member, a hollow drive shaft fordriving said input member, said hollow shaft communicating with saidchamber for directing coolant into said chamber and providing forremoval of said vapor from said chamber, and a water pump communicatingwith said hollow shaft to provide a pressurized cooling medium in saidcooling chamber, said hollow drive shaft having a tube supportedcentrally thereof for conducting vapor from said chamber, said vaporbeing cooled by the cooling medium in the hollow drive shaft externallyof the tube.